When I was much younger, I always assumed that the credit card company ate the loss (as long as it wasn't something insane). "They're a big company, so they can write it off, right?"
Your question made me wonder if this assumption was right or not, so I looked it up, found this web page on Experian's website, and read through the list of events in the "How Do I File a Chargeback?" section. Like a lot of things in life, it seems like my younger self oversimplified things. 
After approving your dispute, the credit card issuer (Citi) can go to the card network (VISA, Mastercard, etc.) in order to get the charge reimbursed. If the card network approves the request, then they talk with the merchant's bank, who either disputes the request or goes to the merchant (FYE) with the dispute. At that point, the merchant either accepts or declines the disputed charge.
If the merchant accepts the request, then they pay for the charge. If the merchant declines the request, then they work with the credit card issuer and their bank to settle the dispute, with the card network having the authority to make the final decision on who pays for the charge.
... Honestly, that all seems like a lot of back-and-forth conversation for a $5 charge, so it wouldn't shock me if Citi just ate the charge. They're still a big company, right? 
For something that small, they likely ate it. For larger amounts, once you are out of the equation the issuer and vendor will try to work it out. This is also one of the reasons that some vendors view chargebacks as a big deal (many times a vendor incurrs a fee/penalty for an approved chargeback). If you have enough chargebacks happening as a vendor you can face AA just like an individual can with a card issuer for something they deem "risky". Some vendors can have their agreements altered, be charged/fined more for chargebacks, or lose the ability to accept the card all together.
For $5, they probably just wrote it off and forgot about it.
